722
FXUS61 KOKX 112013
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
313 PM EST Mon Dec 11 2017
.SYNOPSIS...Low pressure approaches tonight and passes to the
north Tuesday. This intensifying low pressure system will move
into the Canadian Maritimes Tuesday night into Wednesday night.
A weak Alberta Clipper passes to the south on Thursday, followed
by a low pressure system passing off the coast Friday night
into Saturday.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Shortwave tracks across IL and Oh toward the region just ahead
of vigorous shortwave diving out of Canada toward the western
Great Lakes region. At the sfc, two low pressure centers
approach, passing across the Great Lakes region toward western
NY State by Tuesday morning. A warm front/WAA out ahead of the
lows/upper shortwaves will result in an increase in clouds, and
precipitation chances increase after midnight.
Cold air initially across the northeast will warm as the night
progresses. Sfc temperatures may initially fall this evening,
then hold steady before rising overnight as south flow begins to
pick up.
At this time, precip looks to hold off until late at night per
most operational models solutions, and many GEFS members. Across
the interior, a few hours of snow is possible, with very low
chances toward the coast for either a wintry mix or plain rain.
Timing and placement will be the key as low levels warm ahead of
the lows.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Upper trough closes off, as sfc low deepens across NY State and
into New England during this time frame.
QPF looks light, with lower amounts or even trace amounts near
the coast, and higher totals as you head north across the
interior. Would expect interior portions of southern CT, and the
lower Hudson Valley of southeast NY to observe higher qpf up to
a 1/4 of an inch liquid equivalent.
Early in the morning, a snow or rain snow mix will quickly give
way to plain rain as WAA continues, and the lower levels of the
atmosphere warm. With increasing southerly flow, temperatures
warm through the 40s, and coastal locations should warm to
around 50. Will lean toward the warmer guidance, and would not
be surprised to see some temps slightly higher than guidance.
Any precip tapers off as the day progresses, and drier air moves
in behind the low/front by evening thanks to NW flow. With the
upper low in the vicinity, a few snow showers are possible
overnight, but this should be isolated. Gusty NW flow and CAA
will commence.
Temps fall to the upper teens/20s across the region. Quite cold.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Wednesday begins with an upper low over the Northeast and a
deepening surface low entering SE Canada. There could be some snow
showers over eastern LI and SE CT in the morning before the upper
low shifts east and overall lift diminishes. Dry, cold and windy
otherwise. 850mb temperatures will fall to around 15C, but partial
sunshine and a strong downsloping wind should somewhat temper the
cold air mixing down from aloft. Highs expected to range from the
upper 20s well inland to mid 30s for coastal sections. Wind chills
start in the single digits in the morning and average around 20 in
the afternoon. For now it appears that wind gusts should fall short
of advisory levels, but probably not by much, so it`s possible that
an advisory would be needed as the event draws closer. Some coastal
spots might even meet criteria based on sustained winds.
Winds subside Wednesday night and low temperatures will average 5-10
degrees below normal. A clipper low is progged to pass south of us
on Thursday. Models show some track and timing differences as well
as available moisture. Snow from this system may however stretch
north into our region, so will introduce low chances for this into
the forecast for southern sections. Like most clippers, this has the
potential for only light accumulations.
The active weather pattern continues on Friday with an upper trough
axis digging into the Ohio Valley and models showing low pressure
strengthening off the Mid-Atlantic Coast. The trough becomes
negatively tilted Friday night, but not before the low is pushed SE
of the 40N/70W benchmark. Upper jet winds/streaks are not currently
progged in a position to help expand the PCPN shield NW towards us
as they did with the storm this past weekend. Shortwaves embedded
within the longwave upper trough however may help spread PCPN closer
to us. Looks like this would be an all-snow event with best chances
of snow Friday afternoon and night. Too early to go with anything
higher than chance PoPs for this potential event.
A high pressure ridge follows for Saturday with dry weather, then
another low moves through the vicinity of the southern Great
Lakes/Ohio Valley regions on Sunday. Global models disagree on its
evolution and track, but will go with a dry forecast through Sunday.
A better chance of PCPN across the entire region appears to be
Sunday night or Monday as the low shifts east.
&&
.AVIATION /20Z MONDAY THROUGH SATURDAY/...
VFR tonight. A complex area of low pressure passes to the northwest
of the terminals Tuesday.
Cigs fall to MVFR late tonight, mainly after 09z Tuesday in
response to a warm front which pushes north of the area.
With models trending slightly warmer and drier, little if any
snow is expected. However, if precipitation starts a bit
earlier, some wet snow is certainly possible. By 12z any
precipitation should be mainly in the form rain for most
terminals, except KSWF, where precipitation could still be snow
or a mix of rain and snow.
Generally westerly winds today becoming light and southerly this
evening. Wind increases Tuesday morning and gusts become more
frequent with speeds around 20 kt.
A cold frontal passage is expected around 16-19z Tuesday and
winds increase dramatically during the afternoon. Potential
gusts of 25-30 KT+ by evening.
NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90
KJFK TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts 25-30 KT possible later in the afternoon.
KLGA TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts 25-30 KT possible later in the afternoon.
KEWR TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts 25-30 KT possible later in the afternoon.
KTEB TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts to 30 KT possible later in the afternoon.
KHPN TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts to 30 KT possible later in the afternoon.
KISP TAF Comments: No unscheduled amendments expected through
06z. Timing of MVFR and any precipitation Tuesday morning may
be off a few hours. Wind gusts to near 20 KT return Tuesday
morning with gusts to 30 KT possible later in the afternoon.
.OUTLOOK FOR 21Z TUESDAY THROUGH SATURDAY...
.Tuesday...Becoming VFR...SE-SW winds G15-25KT shifting W-NW
around 18z and increasing 25-30 KT by evening.
.Tuesday night-Wednesday...Mainly VFR, with a chance of MVFR in snow
showers. W-NW winds G20-35KT probable.
.Wednesday night-Thursday night...VFR. W-SW winds G15-25KT possible.
.Friday...MVFR possible with snow. W-NW winds G15-20KT possible.
.Saturday...VFR. NW winds G15-20KT possible.
&&
.MARINE...
Winds continue to abate, as seas subside. As such, will cancel
current ocean SCA as high pressure passes. Deepening low
pressure approaches from the west late tonight and Tuesday.
South winds increase, and SCA conditions return during the day
Tuesday all waters. Cannot rule out a galegust or two during
the day, but as a front approaches, winds may temporarily
diminish. By nighttime Tuesday, westerly winds pick up behind
the deepening low as it passes north across New England.
Will issue a GaleWatch for the ocean waters beginning Tuesday
night for increasing winds. Will however, continue SCA for non
ocean waters, in the 25 to 30 kt range.
A galewatch is in effect for all waters Wednesday and Wednesday
night with a strong NW flow behind low pressure strengthening as it
heads towards the Canadian Maritimes. SCA conds will likely continue
into Thursday morning for most of the waters. Sub-SCA conds finally
reach all waters by Thursday night with the pressure gradient
weakening. This relatively tranquil period should continue through
Friday. A coastal storm may then impact the waters Friday night into
Saturday with at least SCA conditions developing.
&&
.HYDROLOGY...
No significant hydrologic impacts expected.
&&
.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time. See our headline news on
the web at: http:/weather.gov/nyc
The Riverhead NOAA Weather Radio Station WXM-80 (162.475 MHz)
is currently out of service. NWS technicians are working with
Verizon to restore service. An estimated time of return to
service is not currently known.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...GaleWatch from Wednesday morning through late Wednesday night
for ANZ330-335-338-340-345.
Small Craft Advisory from 6 AM Tuesday to 6 AM EST Wednesday
for ANZ330-335-338-340-345.
GaleWatch from Tuesday evening through late Wednesday night
for ANZ350-353-355.
Small Craft Advisory from 6 AM to 6 PM EST Tuesday for ANZ350-
353-355.
&&
$$
SYNOPSIS...JC/PW
NEAR TERM...PW
SHORT TERM...PW
LONG TERM...JC
AVIATION...IRD
MARINE...JC/PWHYDROLOGY...JC/PW
EQUIPMENT...